Buffon has been linked with a January move to the Premier League side.
“Buffon 5-1 to join Manchester City? Well, I am not surprised by these offers,” Vialli told Sky Sport Italia.
“The Arabs at the club have plenty of money and I think they want to build a very strong team.
“Buffon is a fundamental player but I think Juve will find it very hard to replace him if he leaves as there is no player on the market at his level who could come in and take his place.
“It could be an intelligent move and if I was Buffon I would certainly consider the deal because €15 million is a lot of money.”